1. Field of Invention
The present invention relates to an optical signal transmission apparatus, an optical signal propagation apparatus, and an optical signal transmission method, and more particularly, to an optical signal transmission apparatus, an optical signal propagation apparatus, and an optical signal transmission method that convert multiple electrical signals into optical signals, and batch-transmit these optical signals via optical fibers.
2. Description of Related Art
An example of a conventional optical signal transmission apparatus will be explained with reference to FIG. 1. In FIG. 1, reference numeral 1 refers to a transmission side LSI composed of a CMOS, Bi-CMOS, bipolar, GaAs or the like which is a logic circuit for processing multiple electric signals separately. Reference numeral 11 refers to a laser driver for amplifying an output electric signal of the transmission side LSI 1. Reference numeral 12 refers to a laser diode or a laser diode array, which generates an optical signal that corresponds to this output electric signal driven by the output electric signal that has been amplified by the laser driver 11. Reference numeral 13 refers to an optical connector. Reference numeral 3 refers to an optical fiber or optical fiber tape. The laser diode 12 is optically coupled with the optical fiber 3 via the optical connector 13. The optical signal generated by the laser diode 12 is transmitted to outside via the optical fiber 3.
Reference numeral 2 refers to a receiver side LSI composed of a CMOS, a Bi-CMOS, bipolar, GaAs or the like which is a logic circuit for processing multiple electric signals separately. Here, reference numeral 22 refers to a photo-diode or a photo diode array. Reference numeral 23 refers to a receiver side optical connector. The photo diode 22 is optically coupled with the optical fiber 3 via the optical connector 23. This photo diode 22 photoelectric-converts the optical signal, which has been transmitted from outside via the optical fiber 3, into an electric current that corresponds to the original electric signal. The output electric current signal of the photo-diode 22 is supplied to a current-voltage conversion circuit 21, which converts the output electric current signal of the photo-diode 22 into a voltage signal. Reference numeral 24 refers to a comparator. The voltage signal output from the current-voltage conversion circuit 21 is applied to one input terminal of the comparator 24. A reference voltage V.sub.ref is applied to the other input terminal of the comparator 24.
As has been explained above, when a signal is transmitted from the transmission side LSI 1 to the receiver side LSI 2 via the optical fiber, the output electric signal of the transmission side LSI1 is input to the laser driver 11. The laser diode 12 is then driven in response to the output signal of the transmission side LSI1. The photo diode 22 receives via the receiver side optical connector 23 the optical signal that has been transmitted via the optical connector 13 and optical fiber 3. The photo diode 22 then generates an electric current signal pulse. The current-voltage conversion circuit 21 converts the electric current signal pulse, which has been generated by the photo-diode 22, into a voltage signal. The comparator then 24 compares the voltage signal with the reference voltage V.sub.ref. The voltage signal is then input as a logic signal to the receiver side LSI 2.
Here, the drive current-emission power characteristic of the laser diode 12 is susceptible changes in temperature. Specifically, the emission power intensity of the laser diode 12 changes as the surrounding temperature of the laser diode 12 and the amount of self-generated heat change. The change in the emission power intensity causes the timing accuracy of the transmission signal to deteriorate. The change in the power source voltage of the laser diode 12 also causes the timing accuracy to deteriorate.